/usr/share/octave/packages/image-2.2.2/imtranslate.m is in octave-image 2.2.2-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 | ## Copyright (C) 2002 Jeff Orchard <jjo@cs.sfu.ca>
##
## This program is free software; you can redistribute it and/or modify it under
## the terms of the GNU General Public License as published by the Free Software
## Foundation; either version 3 of the License, or (at your option) any later
## version.
##
## This program is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
## details.
##
## You should have received a copy of the GNU General Public License along with
## this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{Y}} = imtranslate (@var{M}, @var{x}, @var{y})
## @deftypefnx {Function File} {@var{Y}} = imtranslate (@var{M}, @var{x}, @var{y}, @var{bbox})
## Translate a 2D image by (x,y) using Fourier interpolation.
##
## @var{M} is a matrix, and is translated to the right by @var{X} pixels
## and translated up by @var{Y} pixels.
##
## @var{bbox} can be either 'crop' or 'wrap' (default).
##
## @end deftypefn
function Y = imtranslate (X, a, b, bbox = "wrap")
if ( strcmp(bbox, "crop")==1 )
pre = post = ceil ([a b]);
pre(pre > 0) = 0;
post(post < 0) = 0;
X = padarray (X, abs (pre), "pre");
X = padarray (X, post, "post");
endif
[dimy, dimx] = size(X);
x = fft2(X);
px = exp(-2*pi*i*a*(0:dimx-1)/dimx);
py = exp(-2*pi*i*b*(0:dimy-1)/dimy)'; % actually to correspond to index notation 'b' should be
% replaced with '-b'
% but I do not want to brake previous version compatibility
% note: it also must be done in the cropping iand padding code
P = py * px;
y = x .* P;
Y = real(ifft2(y)); % fft return complex number
% for integer shifts imaginary part is 0
% so real takes care of transfer from complex number to real
if ( strcmp(bbox, "crop")==1 )
Y = Y(ypad(1)+1:dimy-ypad(2) , xpad(1)+1:dimx-xpad(2));
endif
endfunction
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